ejabberd

%%%-------------------------------------------------------------------
%%% @author Evgeny Khramtsov <ekhramtsov@process-one.net>
%%% @copyright (C) 2016, Evgeny Khramtsov
%%% @doc
%%%
%%% @end
%%% Created : 15 Apr 2016 by Evgeny Khramtsov <ekhramtsov@process-one.net>
%%%-------------------------------------------------------------------
-module(mod_mam_mnesia).

-behaviour(mod_mam).

%% API
-export([init/2, remove_user/2, remove_room/3, delete_old_messages/3,
	 extended_fields/0, store/7, write_prefs/4, get_prefs/2, select/8]).

-include_lib("stdlib/include/ms_transform.hrl").
-include("jlib.hrl").
-include("logger.hrl").
-include("mod_mam.hrl").

-define(BIN_GREATER_THAN(A, B),
	((A > B andalso byte_size(A) == byte_size(B))
	 orelse byte_size(A) > byte_size(B))).
-define(BIN_LESS_THAN(A, B),
	((A < B andalso byte_size(A) == byte_size(B))
	 orelse byte_size(A) < byte_size(B))).

-define(TABLE_SIZE_LIMIT, 2000000000). % A bit less than 2 GiB.

%%%===================================================================
%%% API
%%%===================================================================
init(_Host, _Opts) ->
    mnesia:create_table(archive_msg,
			[{disc_only_copies, [node()]},
			 {type, bag},
			 {attributes, record_info(fields, archive_msg)}]),
    mnesia:create_table(archive_prefs,
			[{disc_only_copies, [node()]},
			 {attributes, record_info(fields, archive_prefs)}]).

remove_user(LUser, LServer) ->
    US = {LUser, LServer},
    F = fun () ->
		mnesia:delete({archive_msg, US}),
		mnesia:delete({archive_prefs, US})
	end,
    mnesia:transaction(F).

remove_room(_LServer, LName, LHost) ->
    remove_user(LName, LHost).

delete_old_messages(global, TimeStamp, Type) ->
    mnesia:change_table_copy_type(archive_msg, node(), disc_copies),
    Result = delete_old_user_messages(mnesia:dirty_first(archive_msg), TimeStamp, Type),
    mnesia:change_table_copy_type(archive_msg, node(), disc_only_copies),
    Result.

delete_old_user_messages('$end_of_table', _TimeStamp, _Type) ->
    ok;
delete_old_user_messages(User, TimeStamp, Type) ->
    F = fun() ->
		Msgs = mnesia:read(archive_msg, User),
		Keep = lists:filter(
			 fun(#archive_msg{timestamp = MsgTS,
					  type = MsgType}) ->
				 MsgTS >= TimeStamp orelse (Type /= all andalso
							    Type /= MsgType)
			 end, Msgs),
		if length(Keep) < length(Msgs) ->
			mnesia:delete({archive_msg, User}),
			lists:foreach(fun(Msg) -> mnesia:write(Msg) end, Keep);
		   true ->
			ok
		end
	end,
    case mnesia:transaction(F) of
	{atomic, ok} ->
	    delete_old_user_messages(mnesia:dirty_next(archive_msg, User),
				     TimeStamp, Type);
	{aborted, Err} ->
	    ?ERROR_MSG("Cannot delete old MAM messages: ~s", [Err]),
	    Err
    end.

extended_fields() ->
    [].

store(Pkt, _, {LUser, LServer}, Type, Peer, Nick, _Dir) ->
    case {mnesia:table_info(archive_msg, disc_only_copies),
	  mnesia:table_info(archive_msg, memory)} of
	{[_|_], TableSize} when TableSize > ?TABLE_SIZE_LIMIT ->
	    ?ERROR_MSG("MAM archives too large, won't store message for ~s@~s",
		       [LUser, LServer]),
	    {error, overflow};
	_ ->
	    LPeer = {PUser, PServer, _} = jid:tolower(Peer),
	    TS = p1_time_compat:timestamp(),
	    ID = jlib:integer_to_binary(now_to_usec(TS)),
	    F = fun() ->
			mnesia:write(
			  #archive_msg{us = {LUser, LServer},
				       id = ID,
				       timestamp = TS,
				       peer = LPeer,
				       bare_peer = {PUser, PServer, <<>>},
				       type = Type,
				       nick = Nick,
				       packet = Pkt})
		end,
	    case mnesia:transaction(F) of
		{atomic, ok} ->
		    {ok, ID};
		{aborted, Err} ->
		    ?ERROR_MSG("Cannot add message to MAM archive of ~s@~s: ~s",
			       [LUser, LServer, Err]),
		    Err
	    end
    end.

write_prefs(_LUser, _LServer, Prefs, _ServerHost) ->
    mnesia:dirty_write(Prefs).

get_prefs(LUser, LServer) ->
    case mnesia:dirty_read(archive_prefs, {LUser, LServer}) of
	[Prefs] ->
	    {ok, Prefs};
	_ ->
	    error
    end.

select(_LServer, JidRequestor,
       #jid{luser = LUser, lserver = LServer} = JidArchive,
       Start, End, With, RSM, MsgType) ->
    MS = make_matchspec(LUser, LServer, Start, End, With),
    Msgs = mnesia:dirty_select(archive_msg, MS),
    SortedMsgs = lists:keysort(#archive_msg.timestamp, Msgs),
    {FilteredMsgs, IsComplete} = filter_by_rsm(SortedMsgs, RSM),
    Count = length(Msgs),
    {lists:map(
       fun(Msg) ->
	       {Msg#archive_msg.id,
		jlib:binary_to_integer(Msg#archive_msg.id),
		mod_mam:msg_to_el(Msg, MsgType, JidRequestor, JidArchive)}
       end, FilteredMsgs), IsComplete, Count}.

%%%===================================================================
%%% Internal functions
%%%===================================================================
now_to_usec({MSec, Sec, USec}) ->
    (MSec*1000000 + Sec)*1000000 + USec.

make_matchspec(LUser, LServer, Start, End, {_, _, <<>>} = With) ->
    ets:fun2ms(
      fun(#archive_msg{timestamp = TS,
		       us = US,
		       bare_peer = BPeer} = Msg)
	    when Start =< TS, End >= TS,
		 US == {LUser, LServer},
		 BPeer == With ->
	      Msg
      end);
make_matchspec(LUser, LServer, Start, End, {_, _, _} = With) ->
    ets:fun2ms(
      fun(#archive_msg{timestamp = TS,
		       us = US,
		       peer = Peer} = Msg)
	    when Start =< TS, End >= TS,
		 US == {LUser, LServer},
		 Peer == With ->
	      Msg
      end);
make_matchspec(LUser, LServer, Start, End, none) ->
    ets:fun2ms(
      fun(#archive_msg{timestamp = TS,
		       us = US,
		       peer = Peer} = Msg)
	    when Start =< TS, End >= TS,
		 US == {LUser, LServer} ->
	      Msg
      end).

filter_by_rsm(Msgs, none) ->
    {Msgs, true};
filter_by_rsm(_Msgs, #rsm_in{max = Max}) when Max < 0 ->
    {[], true};
filter_by_rsm(Msgs, #rsm_in{max = Max, direction = Direction, id = ID}) ->
    NewMsgs = case Direction of
		  aft when ID /= <<"">> ->
		      lists:filter(
			fun(#archive_msg{id = I}) ->
				?BIN_GREATER_THAN(I, ID)
			end, Msgs);
		  before when ID /= <<"">> ->
		      lists:foldl(
			fun(#archive_msg{id = I} = Msg, Acc)
				when ?BIN_LESS_THAN(I, ID) ->
				[Msg|Acc];
			   (_, Acc) ->
				Acc
			end, [], Msgs);
		  before when ID == <<"">> ->
		      lists:reverse(Msgs);
		  _ ->
		      Msgs
	      end,
    filter_by_max(NewMsgs, Max).

filter_by_max(Msgs, undefined) ->
    {Msgs, true};
filter_by_max(Msgs, Len) when is_integer(Len), Len >= 0 ->
    {lists:sublist(Msgs, Len), length(Msgs) =< Len};
filter_by_max(_Msgs, _Junk) ->
    {[], true}.